Move on and find someone who has some respect for you.
There was a guy that I thought liked me, but when school started he doesn't even acknowledge my presence and he's hanging around another girl. What should I do?
Understand that there is nothing exclusive about someone showing interest .. He could be interested in you as much as any one of many girls .. His showing interest could just be how he interacts by being polite .. It's how he pursues the interest that sets you apart from others .. If he had moved on then his interest was shallow, superficial and not worth fretting about